The present invention relates to an adhesive sheet to be adhered on a rough surface which is a surface having minute unevenness, and particularly, to an adhesive sheet to be adhered on a rough surface of a porous material.
Mortar, concrete and the like are a porous material and the surface thereof is a rough surface having minute unevenness. When such a porous material used outdoors, rainwater is easily impregnated into inside. The rainwater impregnated into inside of the porous material is, thereafter, gradually evaporated from the surface of the porous material and released as a gas containing water.
When an adhesive sheet having no gas-permeability is disposed on the surface of such a porous material, a gas to be released from the surface of the porous material can not escape from the surface. As a result, the gas remains between the surface of the porous material and the adhesive layer of the adhesive sheet, and swelling of the adhesive sheet occurs.
Japanese Patent Application Laid-Open (JP-A) No. Hei 2-32,180 discloses an adhesive sheet for a mortar plate, slate plate and concrete surface. This adhesive sheet has excellent cushioning property and also relatively excellent adhesion to rough surface.
FIG. 1 is a cross-sectional view of an adhesive sheet of this prior art. This adhesive sheet has structure in which a colored layer 101, liquid blocking layer 102, non-woven fabric layer 103 and adhesive layer 104 are laminated. In use, the adhesive layer 104 adheres to the surface of a porous material such as a mortar plate and the like, on which are laminated the non-woven fabric layer 103, liquid blocking layer 102 and colored layer 101.
In the structure of this adhesive sheet, the non-woven fabric layer 103 is gas-permeable, however, the adhesive layer 104 and liquid blocking layer 102 have poor gas-permeability. Therefore, in such a structure, when a gas containing water is generated from an adherend composed a porous material, this gas resides between the surface of the adherend and the adhesive layer 104, and swelling of the adhesive sheet occurs.
Japanese Patent Application Laid-Open (JP-A) Nos. Hei 6-287,525, Hei B-113,768, Hei 9-157,606 and registered utility model No. 2,503,717 describe an adhesive sheet in which a plurality of convex parts having approximately the same height are disposed on the surface portion of an adhesive layer, and the adhesive layer is endowed with gas-permeability. Such an adhesive sheet can easily let air that has been took in between an adherend and adhesive sheet go, in use.
FIG. 2 is a cross-sectional view showing one example of such a conventional adhesive sheet. This adhesive sheet has structure in which a film substrate layer 201, and an adhesive layer having on the surface part of the layer a plurality of convex parts 203, 203xe2x80x2 having approximately the same height, are laminated. In use, the convex parts 203, 203xe2x80x2 of the adhesive layer 202 are adhered to the surface of the adherend, and on which is laminated the film substrate layer 201.
The adhesive layer, 202 has unevenness on the surface part of the layer.
Therefore, concave parts 204, 204xe2x80x2 interposed by the convex parts 203, 203xe2x80x2 do not adhere to the surface of the adherend and remain as spaces. The remaining spaces form on interface between the adherend and the adhesive layer a continuous channel communicating with outside. This continuous channel can effectively let a gas generated from the adherend go outside of the adhesive sheet. Therefore, in such a structure, even when a gas containing water is generated from an adherend composed of a porous material, swelling of the adhesive sheet does not occur.
However, when unevenness is formed on the surface of the adhesive layer, area on which the adhesive layer contacts with the surface of the adherend decreases. Therefore, adhesive force by which such an adhesive layer adheres to the adherend decreases as compared with an adhesive layer in which unevenness is formed on the surface, In particular, when adhesion is effected on rough surface having minute unevenness, the adhesive layer having unevenness on the surface can not obtain high adhesive force.
In addition, there is also an adhesive sheet in which an aluminum foil is disposed between a substrate layer and an adhesive layer, to suppress mechanically swelling of a film, as an adhesive sheet for concrete surface, namely as a marking film. One example is a marking film xe2x80x9cScotchcal(trademark) film CQ-001xe2x80x9d manufactured by Minnesota Mining and Manufacturing Company (3M) of St. Paul, Minn., USA.
However, this adhesive sheet does not have function which lets a gas generated from the concrete surface go.
The present invention solves the above-described conventional problems by providing an adhesive sheet in which swelling thereof does not occur since it can let a gas generated from an adherend composed of a porous material go outside of the adhesive sheet, and which exhibits high adhesive force to rough surface.
The present invention provides an adhesive sheet which comprises a film substrate layer; a channel breathing layer which has a plurality of convex parts on the surface part of the layer and in which a concave part interposed between said convex parts forms a continuous channel communicating with outside; and a breathing adhesive layer, laminated sequentially in the order.